Conventional spindle motor systems (e.g., including a spindle motor controller) are closed-looped systems that use feedback sources to regulate variations in the velocity of a spindle motor as it tracks a target velocity. The spindle motor systems can be used, for example, in hard disk drives. Servo sector timing marks and back-electromotive-force (BEMF) timing marks from spindle motor windings can be used as feedback sources for control loops (e.g., a frequency-locked-loop (FLL), a phase-locked-loop (PLL)) associated with the spindle motor controller. In conventional systems, servo sector timing marks are not available during a self-servo-write (SSW) process because the servo sector timing marks are not yet written. Therefore, during SSW processes feedback from BEMF pulses can be used to determine spindle motor speed characteristics.
Conventional control loops include low frequency electrical system poles. The low frequency electrical system poles limit the bandwidth of the control loop. Low bandwidth can result in low frequency non-repeatable errors and a slow transient response. A user might find it difficult to use the conventional control loops for high precision applications, such as accurate writing of servo marks on blank disk media in a SSW process. On the other hand, high bandwidth is particularly important for smaller form factor hard disk drives due to a smaller disk diameter and a resultant lower inertia of the rotating disk.